This invention pertains to sewing machines; more particularly, it is concerned with a feed clamping device for retaining the feed regulator of a sewing machine in a fixed position at a time when the feed dogs are in engagement with a work material and urging that work material into a forward or rearwardly motion.
In the prior art there is the U.S. Pat. No. 4,018,172 of Ketterer which discloses a face cam which deflects a clamping plate to create a frictional engagement between a feed regulator and the sewing machine frame in order to inhibit motion thereof during the work material feeding cycle. There is also the U.S. Pat. No. 4,019,450 of Adams which discloses a shiftable member extending between a brake member affixed to the feed regulator shaft and an interposer contacting an eccentric on the feed shaft, arranged so as to hold the feed regulator shaft in a fixed position when the feed dog rises into a work material feeding position. This latter patent also discloses as a second embodiment a bell crank pivoted on a stud fixed to the sewing machine frame to have a first arm thereof forced into engagement with a feed regulator by a second arm thereof. Some difficulties were encountered with these prior art devices. For example, in the patent of Adams, the interposer device required a critical adjustment in order to assure proper operation of the regulator clamp device, which adjustment was subject to change due to wear. The bell crank disclosed in the patent of Adams had no adjustment capability with the result that the bell crank could be a highly stressed part which is also subject to considerable wear. The patent of Ketterer discloses an arrangement which is readily susceptible of erroneous adjustment so as to create an over-stressed condition which could be a problem.
What is required is an arrangement which may be readily assembled and will operate without the wear or over-stress problems found in the prior art.